प्राविधिक – इलेक्ट्रिकल, मेकानिकल र टेलिकम
प्राविधिक – इलेक्ट्रिकल, मेकानिकल र टेलिकम
Technical – Electrical, Mechanical & Telecom · ४,५०० प्रश्न
४,५०० प्रश्न उपलब्ध। मोड छान्नुहोस्:
इलेक्ट्रिकल र टेलिकम: प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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On a base of 10 MVA and 11 kV, an impedance of 6.05 Ω expressed in per unit is:
सही उत्तर: ख) 0.5 pu
Base impedance = kV²/MVA = 121/10 = 12.1 Ω, so Z_pu = 6.05/12.1 = 0.5.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An arc suppression coil (Petersen coil) connected between the neutral and earth is used in:
सही उत्तर: ग) resonant earthing of the neutral
The coil's inductance is tuned to the line's capacitance to earth, so the capacitive earth-fault current is neutralised and arcing faults self-extinguish.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 'wave trap' (line trap) installed at a substation on a transmission line is used for:
सही उत्तर: क) power line carrier communication (blocking high-frequency carrier signals from entering the station)
The wave trap is a parallel-tuned circuit offering high impedance to the carrier frequency while passing 50 Hz power current.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 400 kV line has a surge impedance of 400 Ω. Its surge impedance loading (SIL = V²/Zc) is:
सही उत्तर: घ) 400 MW
SIL = (400 kV)²/400 Ω = 160 000/400 MW = 400 MW.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A transmission line has inductance 1 mH/km and capacitance 0.01 μF/km. Its surge impedance √(L/C) is about:
सही उत्तर: ग) 316 Ω
Zc = √(10⁻³/10⁻⁸) = √(10⁵) ≈ 316 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Compared with an overhead line of the same length and voltage, an underground cable has:
सही उत्तर: ग) a much higher capacitance
The conductors are very close together and separated by solid insulation of high permittivity, so cable capacitance (and charging current) is much greater.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Compared with a radial distributor, a ring main distribution system:
सही उत्तर: ग) maintains supply to consumers even if one section develops a fault
In a ring main each point is fed from two directions, so a faulty section can be isolated without interrupting the rest.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to Kelvin's law, the most economical size of a transmission conductor is the one for which:
सही उत्तर: घ) the annual cost of energy lost equals the annual interest and depreciation on the capital cost of the conductor
A thicker conductor costs more but loses less energy; total annual cost is least when the variable capital charge equals the annual cost of losses.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A distribution feeder has 11.5 kV at its sending end and 11 kV at its receiving end at full load. Its voltage regulation is about:
सही उत्तर: घ) 4.5%
Regulation = (Vs − Vr)/Vr × 100 = 0.5/11 × 100 ≈ 4.5%.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A short transmission line delivers 1000 kW at its receiving end, and the line losses are 50 kW. Its transmission efficiency is about:
सही उत्तर: ख) 95.2%
Efficiency = output/input = 1000/(1000 + 50) ≈ 0.952 = 95.2%.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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